I cut my stock with a mitre saw, worked fine. I also used a hunk of plywood to fill in the space, but I was also installing a mercury recoil reducer. I used polyurethane adhesive instead of epoxy, worked great. Another good tip, once you chop the stock a good table mounted belt sander and even out any poor cuts, I like to shim up the stock on the saw to get it square before cutting it. My fit isn't perfect as my plywood plug moved as the glues was setting. I can fix it later.
You do not always have to use the wood, depend on how much you take off. I did a Win model 70 without ever using a filler.
I also sanded down the seams started with a medium grit and finished with a 600 grit. I used a knife on some of the more pronounced areas.
Krylon fusion paint is excellent, painted mine satin black, kinda wish I used flat.